The Centralab R2-52 Fastatch Type B is a rear dual volume control unit designed for modular potentiometer assembly in vintage electronic equipment. It features a C2 taper specification with a control base diameter of 15/16 inch (7/8 inch). The unit has an overall shaft length of 2 3/8 inches, incorporating a 1/4-inch flat inner section, a 1 3/8-inch top shaft section measuring 3/4 inch round, and a 1-inch bottom shaft section measuring 1/4 inch round.